function Game(ele) {
    this.ele = document.querySelector(ele)
    this.map = new Map(this.ele) 
    this.map.create() 
    this.food = new Food(this.ele)
    this.food.create()
    this.snake = new Snake(this.ele) 
    this.snake.create() 
    this.t=null
}

Game.prototype.start = function(){
    this.t = setInterval(()=>{
        this.snake.move()

        let snakeX = this.snake.snakeObj[0].x * 20
        let snakeY = this.snake.snakeObj[0].y * 20
        let foodX = this.food.foodX
        let foodY = this.food.foodY
        
        if (snakeX == foodX && snakeY == foodY) {
            let last = this.snake.snakeObj[this.snake.snakeObj.length - 1]
            this.snake.snakeObj.push({
                x: last.x, 
                y : last.y, 
                background: last.background, 
                ele:null
            })
            this.snake.create()
            this.food.move()
        }
    }, 150)
Game.prototype.stop = function(){
    clearInterval(this.t)

}
    document.addEventListener('keydown', (e) => {
        e = e || window.event
        console.log(e.keyCode)
        switch (e.keyCode) {
            case 38:
                this.snake.direction = 'top'
                break;
            case 40:
                this.snake.direction = 'bottom'
                break;
            case 37:
                if (this.snake.direction == 'right') {
                    alert('游戏结束')
                }
                this.snake.direction = 'left'
                break;
            case 39:
                this.snake.direction = 'right'
                break;
            default:
                break;
        }
    })
}